Protecting sorting device optics



June 25, 1968 G. R. ANDERSON 3,389,792

PROTECTING SORTING DEVICE OPTICS Filed Nov. 25, 1966 2 Sheets-Sheet l INVENTOR. GERALD R. ANDERSON j M M 2 PHOTO um'r AT TORNE Y June 25, 1968 ca. R. ANDERSON 3,389,792

PROTECTING SORTING DEVICE OPTICS Filed Nov. 25, 1966 2 Sheets-$heet 2 INVENTOR. GERALD R. ANDERSON AT TORNE Y United States Patent "ice 3,389,792 PROTECTING SDRTING DEVICE OPTICS Gerald R. Anderson, Campbell, Calif., assignor to FMC Corporation, San Jose, Calif., a corporation of Delaware Filed Nov. 25, 1966, Ser. No. 597,068 Claims. (Cl. 209111.6)

ABSTRACT OF THE DISCLOSURE A high speed rotary optical head scans a multi-channcl ring of freely falling articles (e.g. rice), for color. A phototube unit provides signals for activating air jet sorting nozzles at each article drop channel. The air jets blow some of the sorted articles toward the optical head lenses but under the invention, these are deflected by a circumferential guard having open, unobstructed windows in front of and rotating with the lenses. The guard windows each having a leading edge which is spaced from the lens by at least a certain critical distance. This distance exceeds article travel along its trajectory during a certain period of time. The articles referred to are articles whose path, if not intercepted, would permit them to strike the lens. The period of time referred to is that time required for the optical head to sweep through the angular extent of the window.

In the preferred embodiment, the guard is in the form of a generally cylindrical plate. The plate has a spiral portion of slightly less than 360 angular extent. The ends of the spiral portion of the guard are joined by a chord section to complete the circumferential extent of the guard.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the sorting of articles by color, and more particularly to the high speed sorting of myriads of articles such as grains of rice, pellets of molding plastic, etc., wherein even slight color imperfections, such as dark or spotted grains, are objectionable.

Description of the prior art The embodiment of the invention to be disclosed in detail is improvement in the sorting devices of Roberts, 3,009,571, and Boyce, 3,236,376, both assigned to the FMC Corporation.

These devices are capable of separating out rice grains that are objectionably dark in color from white grains. Rice must flow through the machine at a relatively high rate and yet substantially all of the grains must be inspected and classified. Rice is cascaded down from a hopper and falls freely across an annular, inspection zone. About 200 reject air nozzles surround the zone. As each grain is falling across the inspection zone it is illuminated and a rotatable, optical scanner sequentially receives the light reflected from each grain and transmits the reflected light to a photosensitive unit. The latter translates the nature of the light reflected from the rice into a reject signal for each dark rice grain. The reject signal operates an air valve at the dark rice grain, which turns on a reject air nozzle. This emits a jet of air that blows the dark rice grain from its normal, falling path into a diverted path for dropping into a reject trough.

With the operating condition outlined above, it can be seen that this machine must not only operate at high speed, but must be very sensitive. Since the machine is to be used commercially, it is undesirable to require frequent adjustment of the electronic signal controls for variations that develop within the machine itself relative to interference in the optical path of the light beam.

3,389,792 Patented June 25, 1968 Thus, an accumulation of dust from the rice grains in the optical path could, in time, cause erratic sorting. Also, the high speed operation required for the service of the type described calls for a relatively strong reject air blast, because very little time is available for operation at the rate through which the grains are processed in the machine.

It has been found that air nozzles of acceptable power impart a trajectory to the rejected rice grains which blows some of them forcibly toward the rotating optical head. When it is considered that millions of rice grains will pass through the machine in a relatively short time, it can be seen that the accumulated effect of rice grains striking the optical objectives could produce a deterioration in the accuracy of the optical sorting.

It has been found in practice, that the interpositioning of a transparent shield in front of the scanning lenses protects the lenses from rice grain damage. However, a shield of this type introduces another problem, namely, the effect of dust from within the chamber, which dust forms a film on the surfaces of the shield. Eventually, this film so reduces the intensity of the light transmitted to the photo sensitive unit that periodic cleaning of the shield is required. Even if the shield is swept by a stream of air for removal of the dust therefrom, as in the aforesaid Boyce Patent 3,236,376, this stream of air has been found inadequate to prevent the development of a film of microscopic particles on the surface of the transparent shield. It has been found that the shields themselves must be cleaned every four hours or so by one of the operators. When a battery of these machines is set up in a processing line, the stopping of a machine, removal, cleaning and replacing the shield may represent a significant portion of the available machine time. Furthermore, the surface of the shield of Boyce can be slowly etched by impact of flying rice grains.

Summary of the invention In accordance with the present invention, the lenses are protected from impact by the rice grains, even though no physical guard element is interposed directly in front of the lenses, that is, even though the lenses are physically as well as optically open to the rice grains under inspection. The optical head of the apparatus to be described which embodies the invention employs two lenses facing the inspection zone. The upper lens is a projection lens for projecting a beam of white light onto the following rice grains in front of the individual reject nozzles. The lower lens is a condensing lens for receiving light reflected from the rice grains under inspection and transmitting it to other optical units and into the photocell unit.

The guard of the preferred embodiment of the invention has open windows at each lens and has a low pitch sp'ral portion of less than 360 extent. The spiral portion is disposed so that the leading edge of each window is spaced radially outwardly from the trailing edge of the window by at least a critical distance. The leading and trailing edges of the spiral portion of the guard are circumferentially completed above and below the Windows by a chord portion of the guard.

The principle is as follows: The selected radial spacing of the leading edge of each window from its trailing edge exceeds the travel of the most potentially damaging rice grains, normally encountered during operation of the apparatus, during the time the optical head rotates through the angular extent of the windows in the guard. Consideration will show that these rice grains are those which will be moving toward the leading edge of a window in the guard. Under the conditions given, the entire window passes in front of the trajectory of these rice grains before they can enter the window. Hence the rice grains harm- "D G lessly strike the guard at the trailing edge of the window.

Machines of the type described usually provide inspection doors at their upper portions which can be opened to check their operation of the apparatus. The guard of the present invention is downwardly conical to cause the rice grains to ricochet therefrom in a downward direction. This renders it safe to open the inspection doors above the reject air nozzles when the machine is operating, without danger from flying rice grains. Of equal or even more importance is the fact that rejected grains do not ricochet back into the falling stream of acceptable grains.

The guard of the present invention also presents a smooth surface to the trajectory of the rice grains, which surface is normal or almost normal to that trajectory. This imparts substantially no tangential motion to the rice grains and so dos not accelerate them further, particularly toward the inspection doors, or into the good rice receiver. Also, this minimizes breakage of the rice grains upon impact with the guard.

Experience has shown in the use of the machine described above for sorting rice that machines will operate as long as one week before cleaning of the lenses is required, as opposed to the requirement of a cleaning cycle every few hours when a physical lens shield is employed. It has also been found that no rice grain-s enter the windows of the guard and that the guard does not break rice grains upon impact.

Brief description of the drawings FIGURE 1 is a vertical section through a rice inspection machine embodying the invention.

FIGURE 2 is a transverse section through the optical head taken on line 2-2 of FIGURE 1.

FIGURE 3 is a fragmentary front elevation of the optical head.

FIGURE 4 is a planned fragmentary section of apparatus taken on line 4-4 of FIGURE 1.

FIGURE 5 is a fragmentary vertical section through the guard and optical head of a modified form of the invention.

FIGURE 6 is a section taken on line 66 of FIG- URE 5.

Description of preferred embodiments The invention will be described in detail in connection with a machine designed for the high speed sorting of grains of rice, pellets of molding plastic, or the like. As seen in FIGURE 1, the machine includes a standard and frame assembly A, which supports a detachable hopper assembly B into which the rice is loaded. At the central portion of the hopper is a lamp assembly L and part of the optics. Grains of rice 10 are loaded into the hopper for sorting fall by gravity in front of an annular ring of reject air nozzles C, there being about 200 of these nozzles. Grains 10 that are not dark, are passed or accepted, and these grains continue falling into a trough 12. Dark grains 101' are rejected, that is, they are given a new trajectory by the associated air nozzle C, and these fall into a reject trough 14. A sweeper assembly S rotates slowly to brush clear the troughs 12 and 14.

A rotating optical scanner 0 is mounted along the axis of the machine and includes means for both directing illuminating light to the rice grains and receiving reflected l ght therefrom. The guard G of the invention surrounds light projecting and receiving lenses of the scanner. Light reflected from the grains is directed down to a photosensitive unit PC which provides reject signals. These signals are distributed to the appropriate air nozzle C by means of a signal distributor assembly D. The interaction of the optical, signal distribution, and reject systern of the apparatus is explained in more detail in the aforesaid Roberts Jr. Patent 3,009,571, incorporated herein by reference.

Those details of the machine necessary for a complete understanding of the invention will now be described briefly. Disposed about the lower inside portion of the standard and frame assembly A are legs projecting radially inwardly from a cylindrical shell 22. At the top of the shell and radially inwardly from its periphery is an annular flange 23 which mounts the ring of air nozzles C. Projecting downwardly from the ring of nozzles is the outer wall 24 of the trough 12. A plate 26 forms the bottoms of both the pass and reject troughs 12, 14. The plate 26 is apertured at 27, 27a to distribute classified articles to pass and reject chutes 28, 30 as seen at the right of FIGURE 1.

The sweeper assembly S clears the troughs and dis tributes the rice into the chutes 28, 30. The sweeper is rotated relatively slowly by a combined sprocket and turntable 32 which is rotatably supported on the frame assembly A by rollers 33, only one of which appears in the drawing. Brushes 34, 36 are mounted on the turntable 32 and sweep the troughs 12, 14 respectively. Projecting upwardly from the zone between the brushes is a classified rice divider wall 38 which rotates with the sweeper assembly. The central portion of the sweeper assembly is spanned by a conical screen 40, across which rejected grains slide and fall into the reject trough 14. The sweeper assembly S is rotated by a motor and chain drive unit 40, 42, the details of which are not critical to the present invention.

Significant details of the hopper and lamp assemblies B, L will now be described. The hopper assembly includes a conical hopper 48 into which grains of rice 10 are fed for sorting. The hopper 48 is supported by legs 49 and a removable mounting ring assembly 50 that rests on top of the frame shell 22. At the central portion of the hopper is a lamp housing 52 supported on three radial tubes 54, one or more of which can serve as air ducts. A rice delivery throat 56 is provided between the mouth of the hopper 48 and the lamp housing 52. Rice falling through this throat slides down along a conical skirt 60 supported on the lamp housing, FIGS. 1 and 2. The conical skirt 60 cooperates with an outer conical skirt 64 depending from the hopper assembly legs 49, and these skirts cooperate to form an annular rice delivery throat 66. Grains of rice continuously fall in front of the nozzles to form a curtain of free falling rice at an annular inspection zone. In FIGURE 1 the grain of rice indicated specially at 10; is shown in front of a nozzle C, which nozzle has been actuated to direct a jet of air to the grain and deflect into the reject trough 14.

Within the lamp housing 52 is a source of white light in the form of a projection lamp that is mounted above condensing lenses 74. These are mounted in an optical tube supported on the lamp housing by means of a flange 76 apertured for the passage of air from a blower 78 connected to the lamp housing mounting tube 54. The other tubes 54 can likewise have blowers if desired, or if not, these tubes will be blocked off.

The rotating part of the optical scanner 0 includes an axially disposed vertical optical tube 80 mounted for rapid rotation within the frame assembly A on bearings 81, 82. These bearings are mounted in a central sleeve 83 forming part of the frame assembly. The optical tube is rotated at 3400 r.p.m. by a motor and timing belt drive 84, 86. The diameter of the annular inspection zone for the rice grains patent is about 32 inches and the diameter of the guard G is about 10 inches, in the embodiment of the invention being described. Thus at 3400 rpm. scanner rotation it can be seen that relatively high linear velocities of the rice grains are involved.

Returning to the description of the optical system, the upper end of the optical tube 80 mounts a collimating lens 87 which directs illuminating light to an inclined mirror 88, which in turn directs the light to a projecting lens 90. This lens is supported in an enlarged cylindrical lens mounting tube portion 91 of the optical tube 80. Light from the rice grains under inspection is reflected by the grains and returned to an objective lens 92 below the projection lens and inclined to the optical axis by the proper angle of incidence. The reflected light is passed down the axis of the optical tube by an inclined mirror 94, passes through a slit 95, which masks the beam of light so that only light from the rice grain under inspection is examined by the unit PC.

This light continues on through a projection lens 99 which directs it to the sensitive element of a phototube, photocell or photomultiplier tube in the unit PC, for operating the reject circuits in accordance with the aforesaid Roberts, J r. patent.

When a dark grain of rice is inspected, the photounit PC emits a reject signal through a wire to the distributor D. The signal is conducted by a brush and commutator assembly 100 to a distributor electrode 101, as seen near the bottom of FIGURE 1. A ring of reject electrodes 102 is provided, there being one electrode for each air nozzle C. Upon the issuance of a reject signal the air between the distributor electrode 101 and the associated reject electrode 102 is ionized, causing a current flow through the wire y, which actuates an electronic trigger mechanism 104 just below the nozzles C. The reject signal is thus sent on as a pulse through a wire 2, connected to the air valve 106 on the proper air nozzle C, that is, the nozzle that happens to be opposite the dark grain of rice r under inspection.

When the valve 106 is thus actuated, a jet of air impinges upon the grain 102' and deflects it out of the normal path, such as that of the grain 10p, and over towards the guard G of the present invention. Quite often, the rejected rice falls down onto the screen and slides into the reject trough 14 without striking the guard G. However, due to the air jet velocity requirements referred to above, grains of rice will often have a trajectory causing them to impinge forcibly against the guard G.

The preferred embodiment of the guard G appears in FIGURE 1 and additional features thereof are shown in FIGURES 2 and 3. In this embodiment of the guard, the most potentially dangerous articles, that is articles most likely to damage one of the lenses 90 or 92, will strike an outer surface of the guard and never enter into the space between the guard and the optical tube portion 91. The guard is formed of a generally cylindrical shell 110 formed of sheet metal or other thin, hard material. The shell has windows 90a and 92a that open towards the lenses 90, 92, respectively. As seen in FIG- URE 1 the guard is mounted upon the end of the optical tube portion 91 by a mounting flange 112. As best seen in the section of FIGURE 2, the guard has a coarse pitch spiral portion 114 which has an angular extent that is encompassed somewhat less than 360. This spiral portion is closed by a chord portion 116, which encompasses substantially half the circumferential extent of the windows 90a, 92a. As seen in FIGURES 1 and 3, the lower portion 118 of the guard is conical, the cone having a very small apex angle. The lower portions is air-sealed at 119 to the optical tube portion 91. As seen in FIGURE 1, a slight gap 120 is provided between the lower end of the guard and the conical screen 40, to prevent rubbing between the guard and the screen as the optical scanner rotates.

Small particles and dust are exhausted from outside of the guard. For this purpose an exhaust blower 126 is mounted in the lower portion of the frame assembly and withdraws air from a pipe 128 connected to a chamber 130 at the upper portion of the fixed sleeve 83. The chamber 130 communicates by means of passages 132 to the space within the conical screens 40. Air supplied by the blower 78 thus passes down through the lamp housing and into the chamber between the guard G and the sorting zone for the rice grains. Some air passes directly through the screen 40, as described. The lenses 90, 92 are in a dead space, but centrifugal force helps prevent dust from settling on the lenses by flinging particles out through the lens windows.

The operation of the guard G will be explained in connection with FIGURE 2 and the trajectory of several grains of rice are illustrated. As indicated in that figure, the periphery of the guard G at the leading edge spiral portion 114 is spaced from the trailing edge of the spiral portion by a selected distance s. This distance is at least equal to, and preferably exceeds slightly, an assumed distance d, also illustrated. The distance d is that through which the most potentially troublesome grain of rice 10a will travel, while the optical scanner sweeps through the angle w, representing the angular extent of the window a.

The grain of rice 10a shown in FIGURE 2 is termed the most potentially troublesome grain, because it is assumed to have the highest velocity, is traveling on a radial path towards the center of the optical head, and reaches the optical head just at the leading edge 90b (FIG. 3) of the window. The dimensions of the parts and the distance s referred to, are so selected that by the time the rice grain 10a has traveled the distance d, the guard will have turned at least through the angle w (FIGURE 2), to bring the radially innermost end of the spiral portion 114 of the guard in front of the trajectory of the grain. Thus the grain will strike the guard at the radially inner end of the spiral harmlessly, and cannot enter the window. Actually, because 114 is spiral, at the leading edge 92b of the window 92 the distance corresponding to the distance s is somewhat small than s. Also shown in FIG- URE 2 is the trajectory of another grain of rice, 10b. This grain is not directed radially and hence even though if the maximum expected velocity is imparted thereto, it is potentially less troublesome. This grain will reach the guard atsome intermediate portion of the window so that the trailing edge of the window will be well past the point of impact with the spiral.

Also shown in FIGURE 2 is the trajectory of a grain of rice 100, on a radial path from a previously actuated nozzle C1. This grain was emitted earlier but arrives at a midportion of the window. Even if it has the velocity of grain 10a, this grain will strike the radial inner portion of the spiral 114.

Experience has shown that when the guard is designed in accordance with these principles, on no occasion will rice enter a window. It will not even enter sufliciently to be struck by the trailing edge of either window. Hence the rice will not be forcibly deflected and accelerated by the guard, and will not be caused to bounce against the rubber inspection doors 65, FIGURE 1. Thus these doors may be open to observe operation of the device without danger of injury from flying grains. Furthermore, if the articles are fragile, since there are no rotating projections to augment their velocity or change their direction in a manner that increases their velocity, the guard does not cause breakage of the grains merely because it is turning rapidly. Also, dark rice grains do not ricochet back into the stream of good rice grains falling into the trough 12. The mode of operation at the lower window 92a in protecting the lens 92 is like that previously described. The distance s shown in FIGURE 2 between the radially outermost portion of the spiral and the radially innermost portion thereof is somewhat less at the lower window 92a. However, this does not alter the basic mode of operation. The circumferential extent of the lower window 92a is less than that of the upper window (FIG. 3), so that the sweep time of the lower window is also less. This reduces the available time of flight of grains during the sweep time. Also, as can be seen from FIGURE 1, the time of flight to the lower window exceeds that to the upper window because the path is longer. Hence, the inclined trajectory grains have a lower terminal velocity, due to retardation of the air during the longer time of flight. This gives the guard more time to turn during flight of the grains.

FIGURES 5 and 6 show a modified form of guard G1 which can be substituted for the guard G, just described. The guard G1 has a thin cylindrical shell 140, the inner wall of which is spaced a distanct 1 (FIGURE 6) from the wall 91 of the optical tube. As in the preferred form of the invention, distance t exceeds the assumed distance d traversed by the most potentially troublesome grain of rice 10a during sweep of the scanner through the window angle. The guard G1 has windows 142, 144 in front of the lenses 90, 92 as in the previous embodiment of the invention.

In this installation, the most troublesome grain of rice would be the grain 10c, approaching the leading edge of the window 142. This grain will pass inside of the shell 140 and will hence forth thereafter continue along its original trajectory, while moving between the shell and the wall of the optical tube 91. The grain is harmlessly trapped, however, because the angular velocity of the optical head is such that in no case can a grain of rice so entering the guard strike either the upper lens 90 or the lower lens 92.

The grains of rice thus trapped within the shell 140 by entering through the upper window 142 are prevented from falling in front of the lower lens 92 by means of a helical ramp 146. These grains thus fall down between the shell and the optical tube along the ramp, but drop off the end of the ramp 148, as seen at the left of FIG- URE 5. The drop off point is below the lower lens 92. The grains thus deposited, fall out onto the screen 40 and roll down into the reject trough 14 as before. A guard ramp 150, is located in the zone of the lower lens 192 to prevent rice grains 10 from bouncing up from the ramp 146 and in front of that lens.

Thus in both embodiments of the invention, although the lenses are unobstructed optically and physically, no rice grains can strike either lens. Any large particles of dust or dirt in the system are withdrawn by the blower system and film formation on the lenses is quite slow, so that the machine can be operated in production for a week or more before the lenses require cleaning.

The inspection door 65 can be opened at any time without danger from flying rice grains. The conical portion 118 of the guard in the preferred embodiment of the invention insures that ricocheting rice grains will not be projected towards the inspection door or into the good rice channel. However, the cylindrical guard G1 of the form shown in FIGURE 6, due to the angle of incidence of the rice grains, does not deflect the grains back towards the inspection door or into the good rice channel, either. No radial projecting surfaces are provided in either form, which might strike rice grains and impart major changes in direction and velocity thereto.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention as set forth in the appended claims.

Having completed a detailed description of the invention so that those skilled in the art could practice the same, I claim:

1. Article sorting apparatus comprising a rotating optical scanner, means for imparting a trajectory to classified articles that leads the articles toward the scanner optics, guard means at said scanner comprising a circumferentially smooth shell surrounding the scanner and providing open window means in front of and spaced from the scanner optics by a selected distance at the leading edge of said window means, said scanner spacing distance exceeding the travel of maximum velocity articles during scanner rotation through the angular extent of said window means.

2. The apparatus of claim 1, wherein said guard includes a coarse pitch spiral portion extending from the leading to the trailing edge of said window means.

3. The apparatus of claim 1, wherein said guard has a spiral portion connected at its ends to a fiat chord portion, the chord portion encompassing a trailing portion of said window means.

4. The apparatus of claim 1, wherein said guard is substantially uniformly spaced from said scanner by said selected distance.

5. The apparatus of claim 4, wherein a helical ramp runs down between said guard and the scanner.

6. Article sorting apparatus comprising means for providing an annular, multi-channel inspection zone of falling articles, air nozzles at the channels, a rotating optical head at the center of said inspection zone, said head comprising a rotating optical element means facing the inspection zone, and a generally cylindrical guard surrounding the optical element means for intercepting the trajectory of articles travelling toward said optical element means; the improvement wherein said guard is apertured to provide open window means in front of the optical means, the guard at the leading edge of the window means being spaced radially from the associated optical means by a distance which exceeds the travel of maximum velocity articles during rotation of the optical head through the angular extent of the window means.

7. The apparatus of claim 6, wherein said guard includes a coarse pitch spiral portion extending from the leading to the trailing edge of said window means.

8. The apparatus of claim 6, wherein said guard has a spiral portion connection at its ends to a flat chord portion, the chord portion encompassing a trailing portion of said window means.

9. The apparatus of claim 6, wherein said guard is substantially uniformly spaced from said scanner by said selected distance.

10. The apparatus of claim 9, wherein a helical ramp runs down between said guard and the scanner.

References Cited UNITED STATES PATENTS ALLEN N. KNOWLES, Primary Examiner. 

